public abstract class Company{
    protected string name;
    public Company(string name){
        this.name = name;
    }

    // 透明模式
    public abstract void Add(Company company);
    public abstract void Remove(Company company);
    // 显示树状结构
    public abstract void Display(int depth);
    // 履行职责
    public abstract void LineOfDuty();
}